FAQs on the Ongoing Gulf of Mexico Dolphin Die-off

What processes are under way to examine the potential effects of the Deepwater Horizon BP (DWHBP) oil spill on marine mammals?

There are multiple processes under way that are investigating the potential effects of the Deepwater Horizon BP (DWHBP) oil spill on marine mammals.

• Under the Oil Pollution Act of 1990, a Natural Resource Damage Assessment (NRDA) is being conducted. The NRDA is the process of collecting and analyzing information to assess the extent of injury to a natural resource and determining the appropriate type and amount of restoration needed to compensate the public for that injury. This includes assessing injuries to marine mammals, their habitat (or ecosystem), and the prey upon which they depend that may have occurred as a result of the DWHBP spill. The NRDA is being conducted by:
  • National Oceanic and Atmospheric Administration (NOAA)
  • U.S. Department of the Interior (DOI)
  • U.S. Environmental Protection Agency (EPA)
  • U.S. Department of Agriculture (USDA)
  • Texas
  • Louisiana
  • Mississippi
  • Alabama
  • Florida
• The U.S. Justice Department is using investigations of these impacts for potential criminal and civil cases related to the DWHBP oil spill. As such, samples and all records/data collected from marine mammal strandings are considered potential evidence in these cases.
• Under the Marine Mammal Protection Act of 1972 (as amended), an Unusual Mortality Event (UME) has been declared for cetaceans (whales and dolphins) in the northern Gulf of Mexico (Texas/ Louisiana border through Franklin County, FL) from February 2010 through the present.

Given the overall complexity of the UME investigation and its overlap with and potential importance to ongoing legal investigations (NRDA, criminal, and civil), all of the different investigative teams are coordinating their activities. This coordination ensures that all data and samples are collected, preserved, and stored appropriately, legally, and using the best scientific methods and are analyzed with the best available scientific tools so that they are useful to all parties interested in the health of marine mammals in the Gulf of Mexico.

What is an Unusual Mortality Event (UME)?

An Unusual Mortality Event (UME) is defined under the Marine Mammal Protection Act as a stranding that is unexpected, involves a significant die-off of any marine mammal population, and demands immediate response. There are seven criteria used to determine whether a mortality event is "unusual." If the Working Group on Marine Mammal Unusual Mortality Events (WGMMUME), a group of marine mammal health experts, determines that an event meets one or more of the criteria, then an official UME is declared.

How many UMEs have previously occurred in the Gulf of Mexico?

19 UMEs have occurred in the Gulf of Mexico (12 of which involved cetaceans; the remaining 7 were specific to manatees only) since 1991, when the marine mammal UME program was established, to the present. There have been 57 formally recognized UMEs in the U.S.

What are the causes of previous UMEs in the Gulf and what is the cause of the current UME?

In the past, causes of UMEs in the Gulf have been definitively attributed to:

• biotoxins (47%)
• infectious diseases (5%)
• ecological factors (11%; manatees only)
• unknown causes (37%)

All of these factors, per the National Marine Fisheries Service's (NMFS) National Contingency Plan for Response to Unusual Marine Mammal Mortality Events [pdf], are being considered as possible reasons for the current UME in the northern Gulf. The direct or indirect effects of the DWHBP oil spill are also being investigated as potential causes or contributing factors for some of the strandings in this UME.

The investigation is ongoing and no definitive cause has yet been identified for the increase in cetacean strandings in the northern Gulf from 2010 to the present.

Are there any preliminary results available at this time for the current UME?

• Many of the stranded animals are too decomposed for complete testing. Only 17% of the animals that stranded have been alive or freshly dead.
• Historically, the two most common causes of unusual mortality events are morbillivirus and marine biotoxins; for example, red tide. Results so far do not point to these as primary causes of deaths in this Unusual Mortality Event.
• Brucella, a bacterium associated with flu-like symptoms in humans, has been identified in some bottlenose dolphins that stranded in the northern Gulf since the start of the UME. In total, 13 of 56 dolphins tested to date were either positive or suspect positive for Brucella.
• At this time, Brucella is a common thread in some of the Unusual Mortality Event animals, particularly the perinates, but does not account for all deaths.
• Prior to this event, Brucella has not been associated with Unusual Mortality Events in marine mammals in the United States. There is a need to assess how long Brucella has been in the Gulf, how long has it caused dolphin illness in the Gulf of Mexico and why northern Gulf of Mexico dolphins might be more susceptible to severe infections.
• On land, Brucella can infect cattle, goats, dogs, and pigs and lead to illness, including abortions. The Center for Disease Control reports that brucellosis in people is rare in the United States, with approximately 100-200 cases per year. Brucella exposure has been found in many marine mammals throughout the world, and it is not clear how easily marine Brucella can infect people.
• Please see the CDC website for more information and the NMFS Marine Mammal Brucella factsheet [pdf].
• The role of the Deepwater Horizon oil spill on stranding rates, diseases, and the death of dolphins during this Unusual Mortality Event remains under investigation.
• Sample and data collection continue and new analyses of samples and data are under way.

When was the current UME declared and what was the chain of events relative to the oil spill?

• March 2010
  The WGMMUME was consulted regarding an increase in strandings in Lake Pontchartrain, Louisiana. As this consultation proceeded an increase in strandings in the wider northern Gulf was also noted that appeared to start in February 2010 but accelerated in March 2010.
• April 20, 2010
  The WGMMUME was in the process of receiving and reviewing information on elevated strandings in the northern Gulf and providing advice on the overall stranding increase when the Deepwater Horizon fire and oil spill occurred.
• April 30, 2010
  The UME consultation was put on hold and the Marine Mammal Stranding Network and partner agencies moved into Oil Spill Response under the direction of the Unified Command. All marine mammal strandings from the Texas/Louisiana border through Apalachicola, Florida were investigated and sampled as though they could potentially be related to the oil spill. Samples were analyzed or have been stored for future analyses.
• November 2, 2010
  Stranding activities from the Texas/Louisiana border through Apalachicola, Florida transitioned out of the response phase under the Unified Command and into a long-term monitoring phase.
• November 2010
  The consultation with the WGMMUME was re-initiated and included all strandings in Louisiana, Mississippi, Alabama, and the Florida panhandle (Alabama border through Franklin County) from February 2010, when rates first started to increase, throughout the oil spill response and into the Fall of 2010, when stranding rates remained well above average.
• December 3, 2010
  An oiled dolphin was found in Louisiana and the "response phase" was re-initiated under the Unified Command for marine mammal strandings for central and eastern Louisiana. This phase requires heightened reporting of stranding information and provides funds to assist with stranding response.
• December 13, 2010
  An UME was officially declared in the northern Gulf of Mexico (Texas/Louisiana border through Franklin County, Florida). The UME covers cetacean strandings from February 2010 through the present, including the recent very young dolphin strandings.
• January 1, 2011-April 30, 2011
  Strandings of premature, stillborn, and neonatal bottlenose dolphins were elevated in the northern Gulf, especially in Mississippi and Alabama.
• May 25, 2011
  “Response phase” ends in central and eastern Louisiana
• May 2011-December 31, 2011
  Strandings of premature, stillborn, and neonatal dolphins returned to average levels; however, cetacean strandings of all size classes continued to be above average for the northern Gulf of Mexico, primarily Alabama, Mississippi, and Louisiana.
• January 1, 2012-March 31, 2012
  Strandings of premature, stillborn, and neonatal bottlenose dolphins were elevated in the northern Gulf but were not as high as 2011.
• April 2012-present
  Strandings of premature, stillborn, and neonatal dolphins have returned to baseline levels; however, cetacean strandings of all size classes continue to be above average for the northern Gulf of Mexico, primarily for Alabama, Mississippi, and Louisiana. The UME is considered ongoing.

How many dolphins have stranded in the UME?

Please see the weekly updates on the Northern Gulf of Mexico UME website. Please note the numbers listed are preliminary and may be subject to change.

Since not all cetaceans that have died will wash ashore and be found, the number reported stranded is likely a fraction of the total number of cetaceans that have died during the UME.

What age classes of dolphins have been impacted?

In general, throughout the region, strandings have been high for all age classes of dolphins. While it is typical to see a peak in strandings of premature, stillborn, and neonatal dolphins (<115cm) in the spring in the northern Gulf of Mexico, the peak observed in 2011, particularly in Mississippi and Alabama was higher than expected. The proportion of stranded bottlenose dolphins <115cm stranded between January and April 2011 was higher than during the spring of 2010 or 2012.

What are the goals of the UME investigation?

There are four goals of any UME investigation, to:

• minimize deaths;
• determine the cause of the event;
• determine the effect of the event on the population; and
• identify the role of physical, chemical, and biological environmental parameters in the event.

NMFS and our Marine Mammal Stranding Network partners have been working throughout this event to collect samples using consistent protocols, archive and preserve samples using chain of custody protocols, and have submitted appropriate samples, as needed, to laboratories.

Have samples collected from marine mammals been analyzed already?

Throughout the oil spill response and UME investigation, some samples were held at the facilities where they were collected, some were shipped for analyses, and others were shipped to be archived until information gained in the investigation indicates that further analyses are needed.

To date, samples have been submitted for analysis from some animals and from some facilities for:

• blood analyses for live animals
• analyses needed for care of live animals
• formalin fixed tissues for histopathology
• tissues to test for morbillivirus, Brucella, and marine biotoxins
• swabs from externally visibly oiled animals for oil confirmation and fingerprinting
• bacterial cultures for pathogen identification from fresh carcasses or live animals
• genetic analyses
• PAH analysis
• Stable isotope analysis
• Teeth for aging of animal
• Stomachs for prey analysis
• records for review of gross findings

Where are the rest of the samples?

Data, record, and sample inventories are being catalogued following chain of custody at each Stranding Network facility, and samples are being shipped to either laboratories for analyses or to the National Marine Mammal Tissue Bank for archiving until such analyses are needed in the investigation. Original data records and photographs are being shipped to the NMFS Laboratory in Miami for review and archiving

Due to the destructive processes used during chemical analyses, samples may be archived while methods are developed and/or decisions are made by the UME investigative team on those tissues and those methods needed.

Given the state of decomposition of many of the carcasses, initial evaluations of the viability of the samples for specific analyses is being done before they are submitted for chemical or some biological analyses. Sample shipment to laboratories will continue as new carcasses come in.

When will these marine mammal samples be analyzed?

The investigative team is taking a tiered approach relying on pathology and epidemiology to guide the direction additional analyses may need to go as we rule in or out physical, chemical or biological factors that may be contributing to or causing these mortalities.

Many of the carcasses have been moderately to severely decomposed, which significantly reduces the ability to perform many analyses. Some sample analyses are not possible given the decomposition of the carcasses.

The initial evaluations are under way and further evaluations will continue as new animals are found or new evidence determines the direction of the investigation. These rigorous investigations may take months, if not years, to complete. However, NOAA will make every effort to make these data available to the public as soon as it is legally and scientifically appropriate and possible.

Is NMFS/NOAA also evaluating live marine mammals in the northern Gulf?

It is crucial that the UME investigative team evaluate what is going on with live cetaceans in areas where elevated strandings have occurred. As such, the UME investigation benefits from ongoing NRDA studies on live animals in coastal areas of the northern Gulf.

What other studies are going on to assess the effects of the Deepwater Horizon BP oil spill on marine mammals?

Shortly after the oil spill response was initiated, the NRDA process for marine mammals began (early May 2010). Under the NRDA, a variety of studies are being conducted to try to determine potential impacts from the spill on marine mammals. These studies have focused on understanding the type, severity, magnitude, and duration of exposure of oceanic, coastal, and estuarine marine mammals to oil. These studies are ongoing and will likely continue for some time until we understand what impacts may have occurred. For coastal and estuarine dolphins, these efforts include:

• Active Surveillance to Detect Strandings in Remote Locations (2011):
  Starting on March 23, 2011, NOAA began weekly helicopter overflights in remote areas and outer islands of central and eastern Louisiana and Mississippi in an effort to enhance detection of stranded cetaceans. This effort is targeted to detect strandings at the traditional Spring peak of calving and stranding for bottlenose dolphins in this area.
• Aerial Surveys (2010 and 2011):
  Surveys include helicopter flights close to the DWHBP spill site and broad-scale aerial surveys over large swaths of the Gulf, including offshore and nearshore components. Surveys are designed to document the distribution, abundance, species, and exposure of marine mammals and turtles relative to oil from the DWHBP.
• Assessment of Injuries to Mississippi and Louisiana Dolphin Stocks (2010 and 2011):
  Studies have been conducted from Spring 2010 through Spring 2011 to assess exposure to oil and changes in fecundity (fertility), survival, abundance, and prevalence of bottlenose dolphin calves in four areas (Barataria Bay and Chandeleur Sound, LA; Mississippi Sound, MS; and St. Joseph Bay, FL).
• Assessment of Sublethal and Chronic Health Impacts on Coastal and Estuarine Bottlenose Dolphins in Barataria Bay, LA and a Reference Site in Sarasota Bay, FL (May and August 2011):
  This study involved the temporary capture and release of dolphins to conduct veterinary exams, including a complete physical exam, conducting an ultrasound of the organs, and collecting blood for analysis. Dolphins were photographed and marked for future identification and tracking, and satellite and VHF radio tags were placed on dolphins in Barataria Bay to track movements, range and preferred habitats. Stories on this study are available on our website: 
  • NOAA conducts dolphin health assessment in Barataria Bay, Louisiana
  • Study by NOAA and Partners Shows Some Gulf Dolphins Severely Ill

Where can I find additional information?

• Northern Gulf of Mexico UME
• Participants in NOAA's National Marine Mammal Stranding Network
• Marine Mammal UMEs
• National Contingency Plan for Response to Unusual Marine Mammal Mortality Events [pdf]
• Working Group for Marine Mammal UMEs
• Natural Resource Damage Assessment for the Deepwater Horizon/BP Oil Spill:
  • Damage Assessment
  • Workplans and Data
  • Mapping the Response to BP Oil Spill in the Gulf of Mexico

Updated: March 27, 2013